Phenomenon: 03 annual output Honda Accord 2.4L car engine idle instability, and the engine failure lights occasionally lit.
    Troubleshooting: for troubleshooting, maintenance personnel found that the engine idling speed in the 700 ~ 1000r / min between the ever-changing, and the engine board on the engine failure lights. After the in-situ acceleration test and the accelerator pedal, the engine speed can only be maintained before the engine speed rises to 1800r / min. When the engine speed reaches 1800r / min or more, the engine speed can be improved smoothly. With the Honda dedicated HDS diagnostic instrument to retrieve the engine fault code, there are two fault codes P0511 and P2195, meaning the idle air control (IAC) valve circuit failure and after the air-fuel ratio (A / F) sensor signal is thin. Clear the fault code and idle learning, road test, test a long time after the absence of idle instability and fault lights lit the phenomenon, maintenance personnel that the fault code is only an occasional fault code, the engine system has been normal, so To the user.
    The second day, the car because of the same failure into the factory, the engine idling instability is more serious, and the engine failure light again. With HDS diagnostic instrument and call out the fault code P0511 and P2195, view the data flow, found that there are four data anomalies: ① throttle position sensor angle between 9% to 15% change. ② The value of the idle control valve varies between 9% and 18%. ③ injection time between 4.67 ~ 10.00ms change, but there will be irregularly 0ms, that is, the phenomenon of fuel injector does not inject. ④ ignition advance angle between 7 ~ 14 ° changes, but will appear irregularly -2 ° and -10 ° and other values.
    From the data flow analysis, abnormal data and fault code P0511 related, in accordance with the maintenance manual P0511 troubleshooting process check, the line connection is no problem, replace the idle control valve, clear the fault code and the idle learning. View the data flow, the data is normal and the engine is working properly, but after a road test, the engine has appeared idle instability failure. The service personnel tried to replace the throttle body, the engine control unit and the petrol pump assembly, but did not troubleshoot.